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Chem 121 > Exam 1 > Flashcards

Exam 1 Flashcards

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1
Q

What is the Law of Composition?

A

Pure substances will contain the same elements in the same mass

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2
Q

The law of constant composition applies to

A

compounds

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3
Q

Define a pure substance

A

Elements and compounds

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4
Q

Define heterogeneous mixture

A

Different composition, properties, and appearance throughout

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5
Q

Define homogeneous mixture

A

Uniform throughout

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6
Q

A combination of sand, salt, and water is an example of a ____ mixture

A

Heterogeneous

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7
Q

A small amount of powdered chocolate and sugar completely dissolve in water is an example of _____

A

A homogeneous mixture

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8
Q

True or false homogeneous mixtures are not easily separated into its components

A

False.

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9
Q

Define physical change

A

Change to appearance

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10
Q

Define chemical change

A

Transformation of a substance into a chemically different substance

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11
Q

Define extensive property

A

Depends on the amount of a substance

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12
Q

What are the examples of an extensive property?

A

Mass, Volume

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13
Q

Define intensive property

A

Does not depend on the amount of a substance

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14
Q

What are the examples of an intensive property?

A

Density, temperature, melting point, boiling point

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15
Q

Of the following which is not an example of a chemical reaction?

  • dissolution of penny in nitric acid
  • condensation of water vapor
  • a burning candle
  • the formation of polyethylene from ethylene
  • the rusting of iron
A

Condensation of water vapor

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16
Q

Which of the following is not an intensive property?

  • density
  • temperature
  • melting point
  • mass
  • boiling point
A

Mass

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17
Q

Which of the following describes an extensive property?

  • melts at 403 K
  • density is 1.04 g/mL
  • red in color
  • is 2.14 moles of mlcs
  • boils at 410 K
A

Is 2.14 moles of molecules

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18
Q

The unit of force in English system is lb*ft/s^2, what is the SI unit for it

A

kg*m/s^2

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19
Q

What are the SI units and they’re measurements?

A 
G       10^9
M       10^6
k        10^3
base    1
d        10^-1
c        10^-2
m       10^-3
mu     10^-6
n        10^-9
p        10^-12
f         10^-15
20
Q

What is the formula for density?

A

d=Mass/Volume

21
Q

What is the SI unit for velocity?

A

m/s

22
Q

What is the symbol for the element sodium?

A

Na

23
Q

What are the postulates of Dalton’s atomic theory?

A
  • All atoms of a given element are identical; the atoms of different elements are different and have different properties
  • Atoms of an element are not changed into different types of atoms by chemical reactions;atoms are neither created nor destroyed
  • Compounds are formed when atoms of more than one elmt combine; a given cmpd always has the same relative number of atoms
  • Each element is composed of atoms
24
Q

Which of the following is not a chemical change?

  • CO2 is produced by the combustion of gasoline
  • Plants make sugar from CO2 and H20
  • Dissolution of a penny in nitric acid
  • The rusting of iron
  • A goldsmith melts a nugget of gold and pulls it into a wire.
A

A goldsmith melts a nugget of gold and pulls it into a wire.

25
Q

Define accuracy

A

Proximity to the actual value

26
Q

Define precision

A

Proximity to obtained values

27
Q

What is the law of multiple proportions?

A

If 2 elements form more than one compound, the masses of B combine with A in a ratio of small numbers

28
Q

Rank the subatomic particles based on size and weight:

A

weight: neutrons>protons>electrons
size:
protons

29
Q

Isotopes are atoms that have the same ___ but differing ___

A

Atomic numbers, mass numbers

30
Q

How do you find the number of neutrons?

A

Atomic mass-atomic number

31
Q

How do you find the number of protons?

A

The atomic number

32
Q

How do you find the number of electrons?

A

The number of protons +/- charge

33
Q

How do you determine a pair of isotopes?

A

Look for the same atomic number with different masses

34
Q

How do you determine an empirical formula?

A

Divide by a common factor to the completely simplified version

35
Q

How do you know if elements will have similar properties?

A

Elements in the same column/part of the same family

36
Q

An element in the lower left corner of the periodic table is

A

definitely a metal

37
Q

When is something an ionic compound?

A

metal +nonmetal

Left+right

38
Q

When is something a covalent compound?

A

nonmetal+nonmetal

right+right

39
Q

How do you find the percentage by mass of an element in a compound?

A
  1. Find the formula weight

2. Divide the desired element by the formula weight.

40
Q

How do you determine the empirical formula of two given percentages of elements?

A
  1. Convert each one to moles
  2. Determine which is the limiting reagent (The smaller one)
  3. Divide the answers from part 1 by the limiting reagent.
  4. Write empirical formula
41
Q

What is a combination reaction?

A

A+B—-> AB

42
Q

What is a decomposition reaction?

A

AB——>A+B

43
Q

What is a combustion reaction?

A

A+O2——–> CO2+H2O

44
Q

When a hydrocarbon burns in air, what component of air reacts?

A

Oxygen

45
Q

How do you find formula weight?

A

Add up the weights of each element multiplied by the amount of each element.

46
Q

How do you find the number of molecules of a compound?

A

Convert g–>mol

mol—>mlcs =avogadro’s

Chem 121 (1 decks)

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